The field of medical imaging has seen significant advances since the time X-Rays were first used to determine anatomical abnormalities. Medical imaging hardware has progressed from modern machines such as Medical Resonance Imaging (MRI) scanners, Computed Tomographic (CT) scanners, and Positron Emission Tomographic (PET) scanners, to multimodality imaging systems such as PET-CT and PET-MRI systems. Because of large amount of image data generated by such modern medical scanners, there has been and remains a need for developing image processing techniques that can automate some or all of the processes to determine the presence of anatomical abnormalities in scanned medical images.
Digital medical images are constructed using raw image data obtained from a scanner. Digital medical images are typically either a two-dimensional (“2-D”) image made of pixel elements or a three-dimensional (“3-D”) image made of volume elements (“voxels”). Such 2-D or 3-D images are processed using medical image recognition techniques to determine the presence of anatomical abnormalities such as cysts, tumors, polyps, etc. Given the amount of image data generated by any given image scan, it is preferable that an automatic technique should point out anatomical features in the selected regions of an image to a doctor for further diagnosis of any disease or condition.
Automatic image processing and recognition of structures within a medical image is generally referred to as Computer-Aided Detection (CAD). A CAD system can process medical images and identify anatomical structures including possible abnormalities for further review. Such possible abnormalities are often called candidates and are considered to be generated by the CAD system based on the medical images.
Bone metastases, or metastatic bone disease, is a type of abnormality that is of major clinical concern. Bone metastases is a class of cancer metastases that results from primary tumor invasion to bone. Although bone-originating cancers are rare, bones are common targets for cancer cells to spread and settle. Metastases from primary tumors are the most common malignant carcinoma involving skeletons. Their clinical relevance arises from the fact that they are often painful to the patients, and affect a patient's quality of life due to their impact on the stability and motility of a patient's skeleton. Diagnosing bone metastases is therefore highly relevant for therapy decisions.
Medical imaging techniques provide important clues to diagnose and evaluate the progress of bone metastases. Bone scintigraphy (or scan) is the current standard of care. Bone scintigraphy is a nuclear scanning test to find certain abnormalities in bone. This test is highly sensitive, fast and easy to read. However, it is not very specific, and therefore requires an additional imaging scan.